Generally, gamma detectors (hereinafter, “detector”) in a positron emission computed tomography (PET) apparatus receive, by a photomultiplier tube, scintillation light that is (scintillation photons, optical photons) emitted when a gamma ray radiated from a subject enters a scintillator, and convert into an electrical signal.
In conventional detectors in the PET apparatus, many of scintillator crystals, a single unit of which is a scintillator crystal, for example, in the size of several millimeters in length, several millimeters in width, and several tens of millimeters in height (thickness), assembled in an array are used. Moreover, a reflective material is arranged between the scintillator crystals to prevent scintillation light generated inside one scintillator crystal from leaking to adjacent scintillator crystals (crosstalk). Therefore, the conventional detectors discretely identify a scintillator crystal in which a scintillation event occurs.
This identification is based on a precondition that output powers of the detector with respect to reception of a specific number of scintillation photons have been known. The PET apparatuses generally perform processing of adjusting the output power by an amplifier, or data processing of correcting the power by software means in a later stage based on this known information.